A virus like particle is an assembly of virus structural proteins that mimics the configuration of a real virus, except that it contains no genetic material. If a person is vaccinated with VLPs then an immune response is generated as if the immune system has been presented with a real virus. However, as the VLPs do not contain any genetic material they are unable to replicate, and as such are harmless to the person who has been vaccinated. However, that person will now be protected against infection by the real (pathogenic) virus. These characteristics mean that the VLP platform has huge potential for use as an extremely effective anti-viral vaccine.

The production of VLPs is not without its problems. In order to produce a functional VLP that effectively mimics a real virus, good yields of multiple virus structural proteins are needed. These must then be correctly assembled into a particle that reproduces the confirmation of the outer shell (capsid) of an infectious virus. The expression system used to produce the particles must be both safe and capable of producing multiple proteins both on a small scale (for testing) and on a larger scale (for vaccine manufacture).

The above requirements mean that VLP production can be a complex and difficult procedure. Unsurprisingly there has recently been considerable interest in the use of the baculovirus expression system for the production of VLP vaccines as it could overcome the above problems. As the FDA has recently licensed a baculovirus manufactured vaccine for use in humans (Cervarix® by GlaxoSmithKline) to protect against HPV this has now made it possible for the baculovirus system to be used more widely for VLP production. There is also significant interest in using the baculovirus system to produce VLPs that can be used to immunize against the influenza virus.